[naturelover]

I have a question relating to finding the concentations of A and B in the sample.

(The question is attached in JPEG format below).

My question is:
4) Find the concentrations of A and B in the sample - the answer is: Ca= 0.082mM and Cb=0.107mM

I sadly can't seem to get back or work out the answers ...

I've tried the calculations myself.. (and i think this is the way to calculate it?)

Ca= 0.82-0.125cb/9.82

0.91=2.16 (0.82-0.125cb/9.82) + 6.8cb
0.91=0.1804-0.02749cb+6.8cb

but the answers I got were all wrong... can anyone please help me solve this or tell me how to calculate it?
thank you!

[Borek]

This is a simple algebra, and the answers given are OK.

Ca= 0.82-0.125cb/9.82

That's wrong. Use parentheses.